1,720,961 research outputs found
Optimal Radio access in femtocell networks : a Bayesian approach
No full textFemtocell networks offer a series of benefits with respect to conventional cellular networks such as better frequency reuse, improved coverage, higher data rates and extended battery life. However, a potential massive deployment of
femto-access points (FAPs) poses a big challenge in terms of Radio Resource Management (RRM), which requires proper radio resource allocation techniques.
Differently from macro base stations, FAP’s are typically installed by the subscribers and maintained without global planning, with no special consideration about traffic demands or interference with other cells, either femto or macro cells.
Hence, a dense deployment of FAP’s might induce an intolerable interference to macro users or to other femto users. Having that in mind, in this work we develop
several algorithms under the common root of the “Bayesian” approach. First, assuming static femto-to-femto interference we establish local coordinating schemes between FAP’s in order to maximize a network social welfare (or conversely, to
minimize a social cost). Then, once having incorporated a model for the macro interferers’ activity, we extend such schemes in the time-frequency domain. On the latter case we start considering a single FAP accessing the radio channel in
the presence of a dynamical interference environment. Then, with the support of Game Theory (GT), we extend the formulation to a multi-FAP scenario where nearby FAP’s react to the strategies of the other FAP’s, still within a dynamical
interference scenario. The multi-user case is first approached using a strategic non-cooperative game formulation. Then we propose a coordination game based on the introduction of a pricing mechanism that exploits the backhaul link to
enable the exchange of parameters (prices) among FAP’s. The numerical simulations show the worthiness of the joint effect of local coordination and interference estimation
Pricing mechanisms for interference management games in femtocell networks based on Markov modeling
No full textThe potential massive deployment of femto access points requires femto-cell networks to be able to take interference under control, possibly through a decentralized mechanism. Within this context, game theory represents a fundamental tool to devise decentralized algorithms for dynamic resource allocation. In this paper, we propose alternative game-theoretic techniques that exploit the backhaul link among femto-access points to set up local coordination games which provide performance advantages with respect to purely competitive games. The proposed optimization techniques incorporate a Markovian model of the interference activity and propose alternative pricing mechanisms to allocate power in the joint time-frequency plane. © 2011 IIMC
Distributed Bayesian pricing for sum-rate maximization in small-cell networks
No full textIn this paper we address the problem of distributed sum-rate maximization in small cell networks in the special case where users have incomplete information about the interfering cross-channels. The sum-rate maximization problem admits a decentralized solution based on pricing mechanism. This requires the exchange of some control parameters (prices) over a common signaling channel. In femtocell networks, this exchange of control data may occur through the wired backhaul (e.g., an ADSL channel) connecting the femto-access points (FAP's). The problem with the implementation of pricing is that it requires knowledge of the cross channels between the interfering nodes and this information typically is not available. In this paper, we address this problem by using only statistical information about the cross-channels. This leads to a Bayesian pricing mechanism. We start modeling the interference mechanism through a directed random graph. Then, we model the interference incorporating the fading statistics and the spatial distribution of the nodes. We provide a closed form expression for the expected value of the pricing term and derive distributed schemes able to converge to a stationary point of the sum-utility function. Finally, we compare the proposed approach to a purely competitive mechanism and to a clairvoyant (gene-aided) scheme. © 2012 IEEE
Optimal resource allocation in femtocell networks based on Markov modeling of interferers' activity
Get PDFFemtocell networks offer a series of advantages with respect to conventional cellular networks. However, a potential massive deployment of femto-access points (FAPs) poses a big challenge in terms of interference management, which requires proper radio resource allocation techniques. In this article, we propose alternative optimal power/bit allocation strategies over a time-frequency frame based on a statistical modeling of the interference activity. Given the lack of knowledge of the interference activity, we assume a Bayesian approach that provides the optimal allocation, conditioned to periodic spectrum sensing, and estimation of the interference activity statistical parameters. We consider first a single FAP accessing the radio channel in the presence of a dynamical interference environment. Then, we extend the formulation to a multi-FAP scenario, where nearby FAP's react to the strategies of the other FAP's, still within a dynamical interference scenario. The multi-user case is first approached using a strategic non-cooperative game formulation. Then, we propose a coordination game based on the introduction of a pricing mechanism that exploits the backhaul link to enable the exchange of parameters (prices) among FAP's
Decentralized interference management in femtocells: A game-theoretic approach
No full textFemtocells are receiving considerable interest in mobile communications as a strategy to overcome the indoor coverage problems as well as to improve the efficiency of current macrocell systems. One of the most critical issues in femtocells is the potential interference between nearby femtocells and from femtocells to macrocells or to mobile handsets. In this work, we illustrate some decentralized strategies for an OFDMA femtocell system, based on game theory, where non-cooperative femtocells self-organize in order to find out the most appropriate access strategy, considering the decision phase and radio access jointly. The strategies illustrated in this work fall within the context of the FREEDOM European Project
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Optimal radio access in femtocell networks based on markov modeling of interferers' activity
No full textOne of the most critical issues in femtocell network deployment is interference management, especially for femtocells sharing the spectrum occupied by conventional cellular networks. In this work we propose and analyze an optimal power allocation strategy based on modeling the interferer's activity as a two-state Markov chain. In the single femto-user access, we show how to maximize the expected value of femto-user rate, averaged over the interference statistical model. Then, we extend the approach to the multiuser case, adopting a game-theoretic formulation to devise decentralized access strategies, particularly suitable in view of potential massive deployment of femto access points. © 2011 IEEE
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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